Polymer Compositions Comprising Broad Molecular Weight Distribution Polypropylene and Articles Therefrom

Abstract

A composition suitable for a film having a 1% secant flexural modulus (MD or TD) of at least 55,000 psi and a dart drop impact of at least 500 g is provided. The composition comprises a broad molecular weight distribution polypropylene with at least 50 mol % propylene and having: a molecular weight distribution (Mw/Mn) greater than 6, a branching index (g′vis) of at least 0.95, and a melt strength of at least 2 cN; and a polyethylene with at least 70 mol % ethylene and having: a density of from 0.910 to 0.923 g/cm3, a melt index (I2) of from 0.1 to 1.2 g/10 min, a melt index ratio (I21/I2) of from 20 to 35, a weight average molecular weight (Mw) of from 150,000 to 400,000 g/mol, and an orthogonal comonomer distribution and/or at least a first peak and at least a second peak in a comonomer distribution analysis.

1 . A film comprising at least a first layer comprising a polymer composition consisting essentially of:
 a polypropylene comprising at least 50 mol % propylene and having an MFR within a range from 0.1 to 6 g/10 min, a molecular weight distribution (M w /M n ) greater than 6, a branching index (g′vis) of at least 0.95, and a melt strength of at least 2 cN determined using an extensional rheometer at 190° C.; and   a polyethylene comprising at least 70 mol % ethylene and having: a density of from 0.910 g/cm 3  to 0.923 g/cm 3 , a melt index (I 2 ) of from 0.1 g/10 min to 1.2 g/10 min, a melt index ratio (I 21 /I 2 ) of from 20 to 35, and an orthogonal comonomer distribution.   
     
     
         2 . The film of  claim 1 , wherein the polypropylene has a M w /M n  from 6 to 18. 
     
     
         3 . The film of  claim 1 , wherein the polypropylene has a melt strength from 2 cN to 80 cN. 
     
     
         4 . The film of  claim 1 , wherein the polypropylene has a peak extensional viscosity (annealed) within a range from 15 kPa·s to 100 kPa·s at a strain rate of 0.01 sec 1  (190° C.). 
     
     
         5 . The film of  claim 1 , wherein the polypropylene comprises at least 90 mol % propylene. 
     
     
         6 . The film of  claim 1 , wherein the polyethylene has a melt strength of from 1 to 25 cN. 
     
     
         7 . The film of  claim 1 , wherein the polypropylene is present in an amount of 30 wt % to 70 wt %, based on the total weight of the composition, and the polyethylene is present in an amount of 30 wt % to 70 wt %, based on the total weight of the composition. 
     
     
         8 . The film of  claim 1 , wherein the polypropylene is present in an amount of 30 wt % to 50 wt %, based on the total weight of the composition, and the polyethylene is present in an amount of 50 wt % to 70 wt %, based on the total weight of the composition. 
     
     
         9 . The film of  claim 1 , having a 1% secant flexural modulus (MD or TD) of at least 55,000 psi and a dart drop of at least 500 g. 
     
     
         10 . The film of  claim 9 , wherein the film has a 1% secant flexural modulus (MD or TD) of at least 65,000 psi and a dart drop of at least 600 g. 
     
     
         11 . The film of  claim 9 , wherein the polymer film has an Elmendorf Tear (MD or TD) within a range from 400 g to 1600 g. 
     
     
         12 . The film of  claim 9 , wherein the polymer film has a haze of less than 30%. 
     
     
         13 . The film of  claim 9 , having an average thickness within a range from greater 80 μm to 1.2 mm. 
     
     
         14 . The film of  claim 9 , further comprising at least a second and a third layer comprising one or more of the polypropylene, the polyethylene and a different polyethylene. 
     
     
         15 . The film of  claim 14 , wherein the first layer is present in an amount of 40 wt % to 70 wt % and the second layer and the third layer are each present in an amount of 15 wt % to 30 wt %. 
     
     
         16 . The film of  claim 14  having a second layer/first layer/third layer structure.